.TH LLSOM_SYNC 8 2024-08-28 Lustre "Lustre Configuration Utilities"
.SH NAME
llsom_sync \- Utility to sync file LSOM xattr.
.SH SYNOPSIS
.SY llsom_sync
.RB { --mdt | -m }\c
.BI = MDT
.RB { --user | -u }\c
.BI = USER_ID
.RB [ --daemonize | -d ]
.RB [ --verbose | -v ]
.RB [ --interval | -i ]
.RB [ --min-age | -a ]
.RB [ --max-cache | -c ]
.RB [ --sync | -s ]
.I LUSTRE_MOUNT_POINT
.YS
.SH DESCRIPTION
.B llsom_sync
is designed to sync file LSOM xattr in the Lustre Filesystem by
using Lustre MDT changelogs.  A changelog user must be registered
(see lctl (8) changelog_register) before using this tool.
.SH OPTIONS
.TP
.BR -m ", " --mdt= \fIMDT
The metadata device which need to be synced the LSOM xattr of files.
A changelog user must be registered for this device.
.TP
.BR -u ", " --user= \fIUSER_ID
The changelog user id for the above MDT device. See lctl(8) changelog_register.
.TP
.B --daemonize
Daemonize the program. In daemon mode, the utility will scan,
process the changelog records and sync the LSOM xattr for files periodically.
.TP
.B --verbose
Produce a verbose output.
.TP
.B --interval
The time interval to scan the Lustre changelog and process the log record in
daemon mode.
.TP
.B --min-age
The time that llsom_sync tool will not try to sync the SOM data for any files
closed less than this many seconds old.
The default min-age value is 600s (10 minutes).
.TP
.B --max-cache
The total memory used for the FID cache which can be with a suffix [KkGgMm].
The default max-cache value is 256MB. For the parameter value < 100, it is
taken as the percentage of total memory size used for the FID cache instead
of the cache size.
.TP
.B --sync
Sync file data to make the dirty data out of cache to ensure the blocks count
is correct when update the file LSOM xattr. This option could hurt server
performance significantly if thousands of fsync requests are sent.
.SH EXAMPLES
Register a changelog consumer for MDT lustre-MDT0000:
.RS
.EX
.B # cl_user=$(ssh root@mds01 lctl --device lustre-MDT0000 changelog_register -n)
.B # echo $cl_user
cl1
.EE
.RE
.PP
After perform some file operations on the Lustre Filesystem with
mount point '/mnt/lustre' and the filesystem undergoes some changes,
sync file LSOM xattr:
.RS
.EX
.B # llsom_sync --mdt=lustre-MDT0000 --user=$cl_user --verbose /mnt/lustre
.EE
.RE
.PP
To deregister the changelog user (e.g. after this example, or if SOM
updates are no longer needed):
.RS
.EX
.B # ssh root@mds01 lctl --device lustre-MDT0000 changelog_deregister $cl_user
.EE
.RE
.SH AVAILABILITY
The
.B llsom_sync
command is part of the
.BR lustre (7)
filesystem package since release 2.12.0
.\" Added in commit v2_11_53_0-60-gcaba6b9af0
.SH SEE ALSO
.BR lustre (7),
.BR lctl (8)
